Controlled power supply circuit



Nov. 8, 1966 J. 5. NABER 3,284,690

CONTROLLED POWER SUPPLY CIRCUIT Filed May 22, 1963 C W Neutral FIG 2 0 Neutral or Common 44 o A Phase L 46 60/ 62 c B Phase J c C Phase INVENTOR.

ATTYS.

United States Patent Office 3,284,690 Patented Nov. 8, 1966 nors Filed May 22, 1963, Ser. No. 282,504 8 Claims. (Cl. 3218) This invention relates to circuits for controlling elec- I trically operated tools and, more particularly, to a system for controlling the duration of energization of an electrical load.

The copending applications of Richard H. Doyle et al., Serial No. 161,651, filed December 22, 1961, now US. Patent 3,141,171, and Serial No. 269,427, filed April 1, 1963, now US. Patent 3,172,121, disclose and describe fastener driving tools in which a winding is momentarily energized to actuate a magnetic armature and blade to engage and set fasteners, such as staples or nails. The operating windings of these tools are preferably energized by direct connection across an undulating or alternating current potential source for a period less than one cycle. The winding draws a very heavy current which supplies the force necessary to drive the fastener While the short duty cycle prevents excessive heating of the tool. However, some applications require greater driving power than can conveniently be provided during a single undulation or half cycle of an alternating current input potential. This is particularly true in area in which the frequency of the potential is high with the resultant decrease in the length of the half cycle period in which the operating winding is energized.

Accordingly, one object of the present invention is to provide a new and improved system for controlling the operation of electrically actuated tools.

Another object is to provide a system for increasing the power developed in a single shot, electrically operated fastener driving tool.

Another object is to provide a circuit for conditioning a single shot, electrically operated fastener driving tool for use with potentials of increased frequencies.

Another object is to provide a circuit for controlling the energization of an electrically operated tool by a plural phase potential source.

Still another object is to provide an arrangement for sequentially energizing a Winding means from the phase voltages of the potential source to provide an operating pulse of increased length.

Another object is to provide a circuit arrangement including a plurality of coupled and sequentially fired gated rectifiers for selectively energizing a single operating winding of a power unit or tool from a plural phase potential source.

In accordance with these and many other objects, an embodiment of the invention comprises an electrically operated power unit or fastener driving tool including an operating winding in which a magnetic armature and a connected fastener driving element are slidably mounted. When the winding is energized, the armature and blade move downwardly to engage and set a fastener supplied to a drive track construction by a suitable magazine assembly. In order to develop adequate power for driving large fasteners, such as nails or brads, while retaining heating of the tool at a relatively low level, this tool has in the past been connected directly across a single phase or undulating potential source for a period less than one cycle.

In certain applications, the power that can be obtained from a single cycle or less of 60 cycle alternating current potential is not suificient to perform the fastener driving operation. Further, in applications in which the frequency of the energy source is greater than 60 cycles, the duration of a single cycle and, accordingly, the longest duration of an energizing pulse for the operating winding is reduced to a point at which satisfactory driving operations can not be performed. In one embodiment of the invention, a pair of controlled conduction devices or gated rectifiers selectively connect the operating winding between a neutral or common conductor of a single phase 220 volt alternating current potential source and each of two output conductors carrying signals 180 out of phase with respect to the neutral or common line. The conduction of one of the gated rectifiers is initiated by a manually actuated control circuit, and the firing of the first rectifier is effective through a coupling circuit to place the second rectifier in a conductive condition at the end of its conduction and in an overlapping relationship therewith so that a single energizing pulse is applied to the operating winding.

In a second embodiment, the operating winding is selectively connected between the neutral or common conductor of a three-phase alternating current potential source and each of the three phase voltages through three controlled conductio-n devices or gated rectifiers. Conduction through the first rectifier is controlled by a manually actuated control circuit, and the remaining two gated rectifiers are rendered conductive in a time spaced but overlapping relation with each other by coupling circuits responsive to the conductive states in the rectifiers. In this manner, the operating winding is provided with a single operating pulse or signal consisting of components of potentials from the three phases of the input potential to provide an elongated operating pulse with increased power. 7

Many other objects and embodiments of the present invention will become apparent from considering the following detailed description in conjunction with the drawings, in which:

FIG. 1 is a schematic circuit diagram of a control circuit embodying the present invention in which an electrically operating tool is energized from a single phase potential source; and

FIG. 2 is a schematic circuit diagram of another embodiment of the invention in which a power unit or tool is selectively energized by a plural phase potential supply.

Referring now more specifically to FIG. 1 of the drawing, therein is illustrated a circuit or system indicated generally as 10 which embodies the present invention. The system 10 includes means for supplying operating pulses or signals of an increased length to an operating winding or solenoid 12 which forms a part of and is constructed in the same manner as the fastener driving tool described in detail in the above-identified copending Doyle et al. applications. The system 10 is adapted for use with a single phase potential source of, for instance, 220 volts. This source includes a common or neutral conductor 14 connected to one terminal of the operating winding 12 and two other conductors 16 and 18 to which volt signals phase shifted from each other with regard to the common or neutral line 14 are applied. The other terminal of the opera-ting Winding 12 is adapted to be connected to the conductor 18 through a controlled condu'ction device or gated silicon rectifier 20 and to the conductor 16 through a controlled conduction device or gated silicon rectifier 22.

To control the selective conductivity of the rectifiers 20 and 22, the system or circuit 10 is provided with a control circuit 24 which is connected to the gate or control electrode of the rectifier 22. The control circuit 24, which is connected between the common or neutral line 14 and one of the input lines 16, preferably is of the construction shown and described in detail in the copending applications of Richard H. Doyle et 'al., Serial No. 161,727, filed December 22, 1961, now US. Patent 3,179,866, and Serial No. 257,677, filed February 11, 1963. In general,-the circuits disclosed in these two applications include means responsive to the manual actuation of a control element, such as a trigger, for supplying an enabling signal to the gate electrode of the rectifier 22 at the beginning of the first positive-going cycle of the input potential occurring following the instant at which the trigger is actuated. The control circuit 24 is also such as to prevent conduction through the rectifier 22 except during the single cycle in which an enabling signal is applied to the gate electrode.

Accordingly, when the gated rectifier 22 is placed in a conductive condition during the interval in which the potential on the neutral or common line 14 is swinging positive with respect to the line 16, the operating winding is directly connected across and is energized by the potential source. In view of the fact that the winding means 12 is primarily an inductive load, the generally sinusoidal waveform of the current flowing through the winding 12 is delayed slightly with respect to the sinusoidal envelope of the applied potential so that the current flow through the solenoid and the gated rectifier 22 tends to persist beyond the point at which the applied potential swings in a negative direction.

To control the gated rectifier 20 so that this rectifier becomes conductive when the neutral conductor 14 swings positive relative to the input conductor 18, a circuit is provided for coupling the gate electrode of the rectifier 20 to the circuit of the rectifier 22. This circuit includes a pulse transformer 26 having a primary winding 26a and a secondary winding 26b. The winding 26a is connected in series with the rectifier 22, and the winding 26b is connected in series between the conductor 18 and the gate electrode of the rectifier 20 through a current limiting resistance 28 and a diode 30 which serves to block reverse gate current. When current flows through the winding 12 and the rectifier 22, this current through the primary winding 26a induces a potential or pulse in the winding 2612 which is applied to the'gate of the rectifier 20. When the applied potential between the conductors 16 and 14 swings in a negative direction and the applied potential between the conductors 14 and 18 swings in a positive direction, the rectifier 22 is placed in a nonconductive condition, and the rectifier 20 is gated into a conductive condition due to the presence of the gate current or signal from the coupling circuit. The gate signal for the control electrode of the rectifier 20 persists to the time which the potential between the conductors 18 and 14 swings in a positive direction because load current through the winding 12 lags the applied potential. Accordingly, the rectifier 20 maintains the pulse passing through the operating winding 12 during the following half cycle to provide an operating signal of increased length for the winding 12.

The pulse transformer 26 can comprise a single turn primary winding 26a capable of carrying the extremely large currents normally supplied to the solenoid 12 and a secondary winding 26b of several hundred turns. In dependence on the load current passed by the rectifier 22, it may be necessary to supply a shunt across the primary winding 26a to reduce the eifects of saturation. An additional technique that is useful in obtaining a positivegoing gating pulse for application to the control electrode of the diode 20 at the beginning of the cycle in which the neutral conductor 14 swings positive relative to the conductor 18 is to reverse the terminals of the secondary winding 26b and utilize the pulse of opposite polarity induced in the coil 26b by the collapsing flux field of the primary winding 26a when conduction through the gated rectifier 22 is terminated. This pulse is generated at the proper time relative to the transitions in the potentials applied between the common conductor 14 and the two input conductors 16 and 18.

The control circuit control the sequential firing of the tWo gated rectifiers 22 and 20 to provide an energizing pulse for the operating winding 12 of the fastener driving tool that approaches a length twice as long as a single cycle. This is obtained by selectively connecting the single phase, out of phase components of the 220 volt input potential to the winding 12 in sequence. In addition, the control circuit 24 insures that the sequential firing of the controlled rectifier 22 and 20 can be triggered only at the beginning of a full half cycle in the manner described in detail in the copending applications to insure that the operating signal provided by the combined pulses can be as long as possible. By using the delay circuit shown in the pending applications, the duration of the energization of the winding 12 could be adjusted to control the driving power.

FIGURE 2 'ot the drawings illustrates a system or circuit 40 which also embodies the present invention and which includes an operating winding 42 of the type disclosed and described in detail in the above-identified Doyle et a1. applications. One side of the winding 412 is connected to the neutral or common conductor 44 of a three-phase, star connected alternating current potential source. This potential source also includes an A-phase conductor 46, a B-phase conductor 48, and a C-phase con ductor 50 which are selectively and sequentially rendered effective to energize the winding 42 under the control of three controlled conduction devices or gated silicon rectifiers 52, 54, and 56. Conduction through the rectifier 52 is controlled by a control circuit 58 which is the same as those shown anddes-cribed in detail in the aboveidentified copending Doyle et al. applications. The cathode of the rectifier 52 is coupled to the gate or control electrode of the rectifier 54 through a coupling circuit 60 that is substantially identical to the coupling circuit shown in FIG. 1. Similarly, the output of the gated rectifier 54 is coupled to the input or gate electrode of the rectifier 56 through a similar coupling circuit 62.

When the power unit or fastener driving tool is to be operated, the control circuit 58 is manually or automatically operated in the manner described above so that a positive-going gate pulse is applied to the control electrode of the rectifier 52 when the potential on the neutral or common conductor 44 swings positive relative to the A- phase conductor 46. At this time, the rectifier 52 is placed in a conductive condition so that current flows through the winding 42, the rectifier 52, and the primary winding of the pulse transformer in the coupling network 60. The rectifier 52 remains in a conductive condition until such time as the B-phase potential between the conductors 44 and48 swings more positive than the potential between the conductors- 44 and 46. At this time, the gate pulse applied to the gate electrode of the rectifier 54 from the coupling circuit 60 places the rectifier 54 in a conductive condition, and conduction through the rectifier 52 is terminated. Thereafter, the load current for the winding 52 flows through the rectifier 54.

The flow of current through the winding 42 and the rectifier 54 energizes the coupling circuit 62 to supply a control signal to the gate electrode of the rectifier 56. Therefore, when the potential between the conductors 50 and 44 become more positive with respect to the conductor 44 than the potential between this conductor and the B-phase conductor 48, the rectifier 56 is placed in a conductive condition and current flow through the rectifier 54 is terminated. Thus, the load or winding 42 is now energized by the potential between the neutral conductor 44 and the C-phase conductor 50. Conduction through the rectifier 56 and the Winding 42 is terminated when this potential swings negative with respect to the common conductor 44.

The control circuit 40 provides means for increasing the power available for driving fasteners by increasing the period of time during which the winding 42 i energized. This is accomplished by sequentially energizing the winding 42 from each of the three phase potentials of the three-phase potential source under the control of the coupled and sequentially fired gated rectifiers 52, 54, and 56. As indicated above, the power developed by the winding 42 can be controlled by delaying the application of the gate pulse to the control electrode of the rectifier 52 in the manner described in the pending Doyle et al. applications. This power can turther be controlled by selectively using only the desired number of phase potentials from the plural phase potential source.

Although the present invention has been described with reference to two illustrative embodiments thereof, it should :be understood that numerous othermodifications and embodiments can be devised by those skilled in the art that will -fall within the spirit and scope of the principles of this invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A circuit for controlling an electrically operated tool comprising a potential source having a common conductor and at least two phase conductors, winding means for operating the tool, a plurality of controlled conduction devices each having a control electrode, each of the devices connecting the winding means between the common conductor and a difierent one of the phase conductors, and control circuit means connected to the control electrodes and operative to place the devices in conduction at spaced times so that the winding means is continuously energized by the potential source.

2. A system for controlling the operation of a tool comprising winding means, a three phase potential source including a neutral conductor and three phase conductors, three controlled conduction devices each connecting the winding means between the neutral conductor and one of the phase conductors, and means \tor placing the devices in conduction in sequence to energize the winding means from each of the phase conductors in sequence.

3. A system for controlling the operation of a tool comprising winding means, a plural phase potential source having a conductor for each phase and a common conductor, a number of controlled conduction devices equal to the number of phases in the potential source, each of the controlled conduction devices connecting the winding means between the common conductor and a difierent one of the phase conductors, and means coupling the controlled conduction devices to place the devices in a conductive condition in synchronism with the related phase voltage.

4. A system for controlling the operation of a tool comprising winding means, a plural phase potential source having a conductor for each phase and a common conductor, a number of controlled con-duction devices equal to the number of phases in the potential source, each of the controlled con-duction devices having a control electrode and adapted to connect the winding means between the common conductor and a different one of the phase conductors, a control circuit coupled to the control electrode of one of the devices for placing the device in conduction to energize the winding means from one of the phases of the potential source, and other circuit means responsive to the energization of the winding means for applying control signals to the control electrodes of the devices in sequence.

5. A circuit for controlling an electrically operated tool comprising a potential source having a common conductor and at least two phase conductors, winding means .for operating the tool, a plurality of controlled conduction devices each having a control electrode, each of the devices connecting the winding means between the common conductor and a diiferent one of the phase conductors, first means actuated when the tool is to be operated for applying a signal to the control electrode of the device connecting the winding means to one of the phase conductors to operate the tool, and means controlled by the one device for controlling the application of a signal to the control electrode of another device to energize the winding means from another phase conductor.

6. A circuit for controlling an electrically operated tool comprising .an undulating potential source having a common conductor .and at least two phase conductors, winding mean for operating the tool, a number of gated rec tifiers equal to the number of phase conductors, each of said gated rectifiers having a gate electrode and being adapted to conduct the winding means between the common conductor and one of the phase conductors, first control means for applying a signal to the gate electrode of one of the rectifiers to place this one rectifier in conduction to connect the winding means between the common conductor and one of the phase conductors during the first complete properly poled cycle of the undulating potential occurring following the actuation of the first control means, and second control means controlled by the one controlled conduction device ttor applying a signal to the gate elect-rode of another rectifier to control this other rectifier to connect the winding means between the common conductor and another one of the phase conductors.

7. The circuit set forth in claim 6 in which the second control means includes inductive means connected in series with the one rectifier for supplying an induced potential to the gate electrode of the other device.

8. The circuit set forth in claim 6 in which the second control means includes both a pulse transformer connected in series with the one rectifier and a unidirectional conducting means connected between the pulse transformer and the gate electrode of the other rectifier.

References Cited by the Examiner UNITED STATES PATENTS 3,132,294 5/1964 Foote 318-138 3,141,171 7/1964 Doyle et a1 227-2 3,172,121 3/1965 Doyle et al 31016 3,179,866 4/1965 Doyle et al. 318- 3,193,733 7/1965 Orsino 317--148.5 3,215,916 11/1965 Hermann 318122 3,241,002 3/1966 Smith 317- 1485 JOHN F. COUCH, Primary Examiner.

W. RAY, Assistant Examiner. 

1. A CIRCUIT FOR CONTROLLING AN ELECTRICALLY OPERATED TOOL COMPRISING A POTENTIAL SOURCE HAVING A COMMON CONDUCTOR AND AT LEAST TWO PHASE CONDUCTORS, WINDING MEANS FOR OPERATING THE TOOL, A PLURALITY OF CONTROLLED CONDUCTION DEVICES EACH HAVING A CONTROL ELECTRODE, EACH OF THE DEVICES CONNECTING THE WINDING MEANS BETWEEN THE COMMON CONDUCTOR AND A DIFFERENT ONE OF THE PHASE CONDUCTORS, AND CONTROL CIRCUIT MEANS CONNECTED TO THE CONTROL ELECTRODES AND OPERATIVE TO PLACE THE DEVICES IN CONDUCTION AT SPACED TIMES SO THAT THE WINDING MEANS IS CONTINUOUSLY ENERGIZED BY THE POTENTIAL SOURCE. 